There are many parts of good writing that are more about style than grammar, and active voice is one of those details. While a paper written in the passive voice can still be grammatically correct, it's almost always better to choose the active voice when writing academic papers. It will make your work easier to read and give your writing a much stronger voice. But how can you tell whether you're getting the voice right?

Terms

Before we get down to the nitty-gritty details, we need to define some grammatical vocabulary:

Verb. A verb is a word that describes an action or a state of being. Basically, a verb is something that you do. If you run, jump, hide, shout, eat, quote, or just are, that's using a verb.

Subject. The subject of a sentence is the thing that performs the action of the sentence. It almost always comes before the verb. For example, in the sentence "Lisa sat on the floor," Lisa is the subject because she is the one sitting. In the sentence "The photograph was viewed by all the students," photograph is the subject because it's what is being viewed.

Direct object. Direct objects receive the action of the verb. In the sentence, "She threw the ball," the word ball is the direct object because it's what's being thrown. You can usually find the direct object by asking "the verb what?" For example, "threw what?" - the ball.

What is active voice?

So just what is voice? In grammatical terms, voice is used to describe who is doing the action in a sentence. In active voice, the subject of the sentence performs the action of the verb.

Lizapicked up the soccer ball and puntedit across the field.

Markdidn't understandthe question, but Arielexplainedit to him.

In each of these example, the subject of the sentence is the one performing the action. Liza picked up the ball, Mike doesn't understand, and Ariel explained.

What is passive voice?

In passive voice, the subject of the sentence is receiving the action of the verb, i.e., the action of the verb is being done to the subject. The subject itself isn't actually doing anything. Instead, in passive voice, the subject of the sentence is pretty much just sitting there while something happens to it. This is done by swapping around what comes before and after the verb and adding a to be verb (is, was, were, etc.).

The soccer ballwas picked up by Liza and punted across the field.

Now the subject of the sentence - the soccer ball - is receiving instead of performing the action (being picked up). Also notice that the direct object of the sentence in active voice (soccer ball) is now the subject of the passive voice sentence, and that the subject (Liza) has been put in a phrase "by..." This will be important when you want to start fixing passive voice. One more example:

The questionwasn't understood by Mark, but itwas explained by Ariel.

Again, note that the direct object has become the subject (question and it), and that the subjects in the active voice sentence are now part of a "by..." phrase.

What's wrong with passive voice?

There's nothing inherently wrong with passive voice - it's grammatically correct, and as long as you use it properly you can still say what you need to say. Passive voice is usually frowned on in professional writing, however, because it's often wordy and vague, which can make your work difficult to read. For example, if your work included the sentence "The suspect was questioned thoroughly," you've left out some key information for the reader: who was doing the questioning? The sentence could be rewritten in the active voice to give the reader the complete picture: "The police questioned the suspect thoroughly."

Passive voice is also not as effective as active voice in writing because it's less forceful. Saying "The British were defeated by the Colonial Army at the Battle of Yorktown" is not as compelling as saying "The Colonial Army defeated the British at the Battle of Yorktown." You want your writing to be energetic and exciting, and using passive voice can make it feel dull.

When can I use passive voice?

Despite its problems, there are some occasions when it's appropriate, or even required, to use passive voice. The most common of these is in scientific writing, when passive voice is used to put distance between the authors and the work being presented.

For example, in a scientific paper, instead of saying "Weconductedexperiments to test the resistance of the bacteria to traditional antibiotics," you would write "Experimentswere conducted to test the resistance of the bacteria to traditional antibiotics." As you can see, the subject of the first sentence (we) is now gone, and there is no one performing the action (conducting experiments) in the passive voice sentence. It might seem a little weird, but it's standard procedure when writing in the sciences so that any sense of personal action or opinion is removed from the work.

Passive voice can also be used when you don't know who is performing the action of the sentence or if you want to deliberately keep that information from the reader. For instance, it's common in crime reports (The carwas broken into at 11pm Monday night.) because it's not known who actually committed the offense.

How do I change sentences from passive to active?

Fortunately, fixing the passive voice in your writing is fairly straightforward. Start by going through your work and looking for sentences that use passive voice - they're usually easy to spot because they have a to be verb like was, were, or are. If you're not sure whether a sentence is in passive voice, ask yourself whether the subject is doing anything. If it isn't, then it's passive voice.

Once you've identified the sentences you need to change, you need to identify who is doing the action. This will usually be included in a "by..." phrase, but it won't always be. Once the main actor is identified, move it to the start of the sentence and adjust the verb accordingly. Often when switching from passive to active voice, the subject of the passive voice sentence can be turned into a direct object.

The testswere graded by the teacher, but she didn't do a very thorough job.

Here, the teacher is doing the action, so she becomes the subject, test becomes a direct object, and the to be verb is dropped.

The teachergradedthe tests, but she didn't do a very thorough job.

Often when there is information missing from a sentence written in the passive voice you'll need to look for context clues to build the sentence using the active voice.

My roommate and I bought a large couch on sale, but we weren't sure where to put it.After some debate, the tablewas moved into the corner to make room for the couch.

Here it's not clear who moved the table, but we can infer from the surrounding sentences that "my roommate and I" moved it. In active voice, the passage reads:

My roommate and I bought a large couch on sale, but we weren't sure where to put it.After some debate, wemovedthe table into the corner to make room for the couch.

Also keep an eye out for sentences that start in the active voice and switch to passive, which is something you'll want to avoid.

Michael wanted to have dessert, but all the cookieshad been eaten by his sister.

In this example, you'd want to rewrite the sentence so that both clauses are in the active voice.

Michael wanted to have dessert, but his sisterhad eaten all the cookies.

Lastly, look out for dangling modifiers, which are phrases that modify the missing subjects of passive voice sentences.

Unable to find her purse, the policewere called from a payphone.

The phrase "unable to find her purse" is dangling here because it modifies the person who's calling from a payphone - someone who isn't named in the sentence. To rewrite you need to make it active and include the person performing the action:

Unable to find her purse, the womancalledthe police from a payphone.

A few more examples:

After the movie was over, the theatrewas quickly cleaned for the next showing.

After the movie was over, the staff quickly cleanedthe theatre for the next showing.

The chairwas broken, but Sarah says it wasn't her.

Somebodybrokethe chair, but Sarah says it wasn't her.

The bookis being read by most of the class, but a few students are just going to watch the movie.

Most of the classis readingthe book, but a few students are just going to watch the movie.

The foodwas brought to the table, but she wasn't hungry any more.

The waiterbroughtthe food to the table, but she wasn't hungry any more.